4-phase DS-CDMA performance over LEOS/MEOS channels

Title4-phase DS-CDMA performance over LEOS/MEOS channels
Publication TypeConference Paper
Year of Publication1995
AuthorsKerr, R. W., and V. K. Bhargava
Conference NameCommunications, Computers, and Signal Processing, 1995. Proceedings. IEEE Pacific Rim Conference on
Pagination433 -436
Date Publishedmay.
Keywords4-phase DS-CDMA performance, 4-phase spreading sequence, binary Gold sequences, binary sequences, channel model, code division multiple access, downlink performance, elevation angle, error statistics, fading, fading satellite channel, Gaussian environment, in-phase channel, LEOS/MEOS channels, lognormal shadowing, multiple access system, near optimum correlation properties, nongeostationary satellite channel, QPSK modulation, quadrature channel, quadrature phase shift keying, Rician channels, Rician fading, satellite communication, satellite links, spread spectrum communication, symbol error rate upper bound

In this paper, we investigate the downlink performance of DS-CDMA using QPSK modulation and 4-phase spreading sequence in a fading satellite channel. Two different types of spreading sequences will be evaluated. One type of sequence construction will be to use two binary sequences; one for the in-phase channel and the other for the quadrature channel. The binary sequences will be binary Gold sequences. The other type of sequence will utilize sequences from GF(4) which have near optimum correlation properties. The 4-phase sequences have been shown to increase the number of users of a multiple access system by 50% in a Gaussian environment. We investigate the performance of the above sequences in a non-geostationary satellite channel. This channel model for non-geostationary satellites is characterized by Rician fading and lognormal shadowing where the fading/shadowing characteristics depend on the elevation angle of the satellite. The upper bound on the symbol error rate (SER) is derived and is computed for both a LEO and MEO system


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